Patent Literature 1 discloses an example of an instrument for treating hemorrhoids. This treatment instrument comprises a tubular main unit formed of soft plastic; and a chemical heat-generation unit contained in the main unit. When used, air is introduced into the treatment instrument to heat the heat-generation unit, and the treatment instrument is inserted in the anus of the patient. As a result, the hemorrhoid area, i.e., the vicinity of anus is warmed, thereby relieving the symptom of hemorrhoids.